When I'm riding the bike there are no lights on, but when I shut the bike off the battery charge light comes on.
I went ahead and purchased a new battery but still have the same problem.
I will be checking voltage tonight when I get home.

Had work been done on the Brick shortly before this happened?

What's the problem? When the bike is not running that light should be on.

Does the light stay on when the key is turned off?

It's actually an alternator warning light, not battery.

Here's how it works:

One side of the bulb is wired to switched power from the battery. 12.x volts.

The other bulb terminal connects to a blue wire that monitors alternator output.

When the bike is turned on but not running there's 12.x volts at the battery terminal of the bulb and zero volts from the alternator so the bulb illuminates.

When the bike is turned on and running there's 12.x volts at the battery terminal and 13-14 volts from the alternator so the net voltage across the bulb is only a volt or so so it does not illuminate.

If that bulb lights up with ignition off... replace the regulator on the back of the alternator. Go to Tills.de. Its actually quite cheap.

92KK 84WW Olaf wrote:If that bulb lights up with ignition off... replace the regulator on the back of the alternator. Go to Tills.de. Its actually quite cheap.

It should not be possible for the bulb to illuminate with the ignition off. With the ignition off there should be no power to the cluster (green/black wire from Fuse 1 - switched power.) With the ignition off the green/black wire to the instrument cluster is an OPEN CIRCUIT.

It wouldn't matter if the alternator's blue wire were putting out 0V, 12V or 1,000V. Current does not flow through an open circuit and would not illuminate the bulb.

The ONLY power to the cluster with the ignition off is to the LCD clock via the red/white wire from Fuse 3. (Unswitched power.)

Correction: On a 94+ K1100 cluster the power on Pin 6 is a solid green wire from the ignition switch.  (On 93 and earlier Ks it was green/black from Fuse 1.)

For that bulb to illuminate with they key off on a 94-96 the ignition switch would have to be messed up to illuminate the alt warning bulb because that green wire should be an open circuit with the ignition switch in the off position.

duck wrote:It should not be possible for the bulb to illuminate with the ignition off. With the ignition off there should be no power to the cluster (green/black wire from Fuse 1 - switched power.)

In a perfect world, perhaps that's correct; however, the alternator is wired to battery+ and the instrument cluster wiring is grounded so it seems possible that if voltage gets past a failed diode in the alternator, it can light that bulb—at least that's what I've read in numerous explanations concerning both motorcycles and autos having this ignition-switch-off/battery-light-on symptom. Take this one for example. Earlier in that thread, the diagnostic method is to disconnect or unplug the wire attached to the B+ alternator terminal while the light is on  and the ignition switch is turned to Off. If the light goes off, the alternator is the problem. That's easy enough to do before you disassemble the ignition switch, which can be unexpectedly tedious, and often must be done while taking alternating courses of both stimulants and relaxants.

Laitch wrote:

duck wrote:It should not be possible for the bulb to illuminate with the ignition off. With the ignition off there should be no power to the cluster (green/black wire from Fuse 1 - switched power.)

In a perfect world, perhaps that's correct; however, the alternator is wired to battery+ and the instrument cluster wiring is grounded so it seems possible that if voltage gets past a failed diode in the alternator, it can light that bulb—at least that's what I've read in numerous explanations concerning both motorcycles and autos having this ignition-switch-off/battery-light-on symptom. Take this one for example. Earlier in that thread, the diagnostic method is to disconnect or unplug the wire attached to the B+ alternator terminal while the light is on  and the ignition switch is turned to Off. If the light goes off, the alternator is the problem. That's easy enough to do before you disassemble the ignition switch, which can be unexpectedly tedious, and often must be done while taking alternating courses of both stimulants and relaxants.

On a 94+ K1100 If the ignition switch is off and working then there is an OPEN CIRCUIT to one terminal of the bulb and it's PHYSICALLY IMPOSSIBLE for that bulb to illuminate. What happens on some random car has NO impact on that.

BASIC ELECTRONICS: If there is not a path for electrons to flow (a.k.a. open circuit) then a bulb cannot and will not illuminate - ever.

The light shouldn't glow with the ignition off, but it does, so something is wrong.

It might be possible for the alternator light to glow with the ignition off, if the alternator is faulty cause the power to it also provides power to other lights in the cluster, so another circuit could be found.

The light needs power and earth to glow, normally with ignition on, engine off, it gets power from the cluster and earth from the blue wire, so it glows. With engine running it gets positive on both sides, so the light goes out.

One thing would be to clamp a test light to battery positive and probe to the terminal for the blue wire disconnected, the test light should glow. Check in the dark if any of the other lights also glow (for the possibility of being in series) but probably therefore very dimly, for example the oil pressure light. So possibly opposite to normal, positive from the alternator and earth from one of the other lights, through the positive of the instrument cluster.

BASIC ELECTRONICS: If there is not a path for electrons to flow (a.k.a. open circuit) then a bulb cannot and will not illuminate - ever.

That is sage observation if there ever was one.

Thanks for the illumination
Pulled fuse # 3 light still on
Pulled blue wire off of alternator light goes off.
If the alternator is still working what would be it's output at idle?
Thanks again.

So I checked the voltage' and the alternator
is putting out 13 volts at 3500 rpms.
I was planning a trip this weekend of a 1000 mile round trip. I'm not able to get the parts to repair the alternator
before the trip. Hopefully the alternator will not go completely out before I get back.
Thanks Again

diveshadow wrote:So I checked the voltage' and the alternatois putting out 13 volts at 3500 rpms
Pulled fuse # 3 light still on

That is borderline output.  It might not be enough to keep the battery fully charged under load. When you've parked, that instrument cluster light needs to shut off or the battery will eventually discharge completely. Too many discharges and you'll need a new battery. I believe it's likely the battery will fail completely at some time during the trip, but denial is one of my favorite coping strategies so I'm pulling for you 100%.

The information at the link in Reply #7 seems to indicate disconnecting the red wire at B+ terminal, not the blue, for the test with the light-on/ignition switch-off. If the light shuts off, the alternator is the problem. Clearly, the local waterfowl isn't supportive of that idea.

I've installed a toggle switch to disconnect the battery when I stop.
At the worst I'll have to purchase another battery before I get back.
Thanks for the encouragement

diveshadow wrote:At the worst I'll have to purchase another battery before I get back.

Hope springs eternal! This is next-level denial. I'm impressed!   
Keep us apprised. Post some photos of your trip in the General Rides or K-bike pictures sections.

If that bulb illuminates with the ignition switch off then your ignition switch is the problem. It should not be sending 12V to that bulb via the green wire when it is in the off position.

duck wrote:If that bulb illuminates with the ignition switch off then your ignition switch is the problem. It should not be sending 12V to that bulb via the green wire when it is in the off position.

Why do you ignore the possibility that power might be coming from the alternator, as Latch suggests? that could explain why the alternator light comes on. If it was getting power from the ignition switch, that would be enough to make you go, hmmmm, then why isn't the oil pressure light on, or say the neutral light?

They're some of the reasons I think Laitch's suggestion is a better fit for the symptoms.

daveyson wrote:Why do you ignore . . .

Isn't riding your Brick exciting enough for you?

The reason I made the suggestion to change the regulator on the alternator is I had this problem on a K bike about 10 years back. The only light on was the alternator light and my thought was if its an ignition problem there will be other lights on.

Changing the regulator cured the problem. 13V output is already flagging a problem at the alternator and changing the regulator is as simple as it gets.

The regulator is incorporated into the brush pack. It is easily changed out, it can be done in situ no need to remove the alternator.
Regards Martin.

Laitch wrote:

daveyson wrote:Why do you ignore . . .

Isn't riding your Brick exciting enough for you?

Sorry another example of my crappy English. Probably l should have said "Don't forget the possibility of..."

Olaf, that's good to know, that would be an even better solution, almost too easy.

Installed new alternator 
Bike  is charging correctly:cheers:

My alternator stop charging completely on the first leg of my trip. We were able to complete a 1100 mile trip by changing out the battery several times throughout the trip.
When we made it to our half way point I did pull the regulator and checked the alternator . Alternator was bad but I could not get one until I was back in Florida. So swapping out batteries on the trip home. New alternator in and ready for another trip.

A very helpful fact that proved to be useful was when the ABS lights start flashing I had five to six minutes before the engine would shut off due to insufficient battery power.

Excellent summary, diveshadow.